4.9-stable review patch. If anyone has any objections, please let me know.
------------------ From: Sebastian Andrzej Siewior <[email protected]> commit 40da1b11f01e43aad1aa6cea64681b6125e8a2a7 upstream. If a custom CPU target is specified and that one is not available _or_ can't be interrupted then the code returns to userland without dropping a lock as notices by lockdep: |echo 133 > /sys/devices/system/cpu/cpu7/hotplug/target | ================================================ | [ BUG: lock held when returning to user space! ] | ------------------------------------------------ | bash/503 is leaving the kernel with locks still held! | 1 lock held by bash/503: | #0: (device_hotplug_lock){+.+...}, at: [<ffffffff815b5650>] lock_device_hotplug_sysfs+0x10/0x40 So release the lock then. Fixes: 757c989b9994 ("cpu/hotplug: Make target state writeable") Signed-off-by: Sebastian Andrzej Siewior <[email protected]> Signed-off-by: Thomas Gleixner <[email protected]> Link: http://lkml.kernel.org/r/[email protected] Signed-off-by: Greg Kroah-Hartman <[email protected]> --- kernel/cpu.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) --- a/kernel/cpu.c +++ b/kernel/cpu.c @@ -1765,13 +1765,13 @@ static ssize_t write_cpuhp_target(struct ret = !sp->name || sp->cant_stop ? -EINVAL : 0; mutex_unlock(&cpuhp_state_mutex); if (ret) - return ret; + goto out; if (st->state < target) ret = do_cpu_up(dev->id, target); else ret = do_cpu_down(dev->id, target); - +out: unlock_device_hotplug(); return ret ? ret : count; }
